Hob-grinding machine



1927. Feb s c. KNowLEs HOB GRINDING MACHINE 7 Sheets-lShe'et 1 Filed April 9, 1924 rsi.

A INVEIITGR TTHHNEY 1927. 1,617,159' Feb 8 c. KNowLEs nos GRINDING MACHINE Y Filed April 9, 1924 v '7' sheetssheet 2 cr, c3

INVENTGR wvw A WWW 37% ATTRNEY 1927. Feb 8 c. KNowLEs HOB GRINDING MACHINE Filed April 9, 1924 7 Sheets-Sheet 5- ATTQRNEY eb 8 c. KNowLEs HOB GRINDING MACHINE 7 SheetsJ-She-et 4 .Filed April 9, 1924 INVENTGR maffwwz FIV/74 Me ATTRNEY .w SMN w my 159, Feb' 8 1927 c. KNoWLEs p HOB GRINDING MACHINE l Filed April 9, 1924 '7 Sheetsj-She'et 5 221 315, IN1/Ewan zes mofwws A TTHNEV 1927.- I Feb 8? c. KNowLEs HOB GRINDING MACHINE Filed April 9', 1924v 7 Shegts-Sheet 6 7 sheets-sheet 'v Filed April 9, 1924 SWW ATTBHNEY f Patented Feb. 8, 1927..

. UNITED STATES PATENT "Fisica,

`CAILIROI'JL KNOWLES, 0F HARTFORD, CONNECTICUT,`.ASSIGNOB TO PRATT & WHITNEY COMPANY, OF NEW YORK, N.4 Y., .A CORPORATION/ F NEW JERSEY.

HOB-GRINDING MACHINE.

Application med april s, 1924. serial No. 705,250.

My invention relates to grinding ma-W the line tangent to the helix. Inasmuch ,as

chines and particularly to machines fonffthe involute helicoid is formed by lines tangrinding hobs.

One object of my invention is to provide a hob grinding machine that shall be automatic in operation and that shall rind the sides of the hob teeth to involute elicoids.

Another object of my invention is to provide a hob grinding machine of the above indicated character that. shall control the starting and the stopping of the relieving movements of a grinding wheel slide in accordance with the movement of a blank carrying carriage.

Another object of my invention is to provide a hob grinding machine having a rotating hob mounted on a carriage and a grinding wheel mounted on a transversely movable slide, that shall stop the relieving movements of the slide and withdraw the wheel from engagement with the blankwhen the blank carrying carriage is at one end of its movement, and that shall start the relievin movements of the slide and move the whee into engagement with the blank when the blank carrying carriage is at the other end of its movement.

A further object of my invention is to provide a hob grinding machine that shall hob teeth, that shall have improved means for rotating the hob while moving the blank carrying carriage, and that shall have improved means for feeding-the wheel slide and for controlling the relieving movements.

In the art of grinding, it is well known that it is difficult to grind a continuous screw thread with any Vdegree of accuracy unless the lead of the thread is very small. However, it is a relatively simple matter to grind a surface which is in the form of an involute helicoid. The properties of involute helicoids are discussed at some length in the patent to Ernest Wildhaber, No. 1.571,359 granted February 2, 1926, and in the patent to Earle Buckingham, No. 1,540',- 757 granted June 9, 1925. In view of the complete disclosure in the above patents an extended description of the involute helicoid will not'be given in this application. l

An involute helicoid may be considered as the surface formed by continuously advancing a line along a helix' while maintaining form involute helicoids on the sides of theV lane may be provided which includes any ine which is tangent to the helix. Therefore, it is apparent that the grindin of/an involute hellcoid is al relatively Simp e matter. However, it is impo:sible to accurately grind a continuous-screw thread with any degree of accuracy unless the lead of the thread. is relatively small. 'lhe reason for the difficulty in grinding a screw surface is the inability of the grinding wheel to cut alon the exact line by which the thread was initially formed.

In a machine constructed in accordance with my invention, a rotating blank is mounted on a carriage and a grinding wheel is vmounted on a slide' which is movable transversely with respect to the blank. A set of gearing, which is carried by the carriage, is operated from the main frame of the grinding machine and serves not onl to rotate the blank but also to effect longltudinal movement of the carriage. The gearing carried by the :carriage iscontinuous and effects, as heretofore set forth, not only the rotation of the blank but also operates a feed screw which is carried by the blank supporting carriage. The feed screw engages a nut which is secured to the main frame of the machine.v

The wheel slide is subjected to a resilient force tending to move vit away from the blank and is operated by means of a cam, member toeft'ect relieving movements. An adjustable slide, which carries a projecting lug, serves to connect the relieving cam member to the relieving slide. At one end of the movement of the carriage, the adjustff-gent to a helix, it is apparent aI grindingY able slide is so operated as to disconnect the relieving cam from the relieving slide and accordingly to prevent any relieving movements. At such time, the relieving slide is moved away from the blank by the resilient means above mentioned. At the other end of the carriage movement, the adjustable riage is automatic in its operation. The

carriage moves in one direction in accord- Figure 1 is a front elevational view of a machine constructed in accordance with my invention.

Fig. 2 is a plan view of the machine shown in Fig. 1.

'Fig. 3 is a sectional view along the line 3 3. of Fig. 2.

Fig. 4 is a` sectional view along the line 4 4 of Fig..2.

Fig. 5 is a partial end view of the ma-` chine showing the gearing connected to the headstock spmdle.

Fig. 6 is an end view of the machine from the right of Fig. 1 and shows certain partsin section.

Fig. 7 is a view of the cam mechanism for controlling the relieving slide andy the carriage. p

Fig. 8 is an end View of shown in Fig. 7.

Fig. 9 is a sectional view along the line 9 9 of Fig. 7.

F ig.' 10 is a detail View of the means for accentuating the positions of the cam drum.

Fig. 11 is a view from the rear of the machine. U

Fig. 12 is a sectional view through the cam slide along the line 12 12 of Fig. 3.

Fig. 13 is a plan view, partially in section, of one mechanism for adjusting the slides.

Fig. 14 is a sectional View along the line 14-14 of Fig. 13.

Fig. 15 is a plan view of the wheel dressing plate.

Referring to the the mechanism drawings, a machine is illustrated comprising a main frame 1, having a blank carrying carriage 2 mounted thereon. The carriage 2 is fitted to suitable ways 3 and 4 `which are formed on the main frame 1. The carriage 2 is provided with a headstock 5 and a tailstock 6. The headstock 5 is secured to the carriage and the tailstock 6 is` adjustable along the carriage. Preferably suitable bolts 7`are provided for holding the tailstock 6 inv position on the ways which are formed on the carriage. A

' lever 8, which is'spring retracted, is provided for longitudinally moving the tailstock center 9 to mount a blank in position. The carriage 2 is moved by power supplied lto a pulley 10. The pulley is rotatably mounted on a shaft 1'1 which has bearings 12 and a bearing in the bracket 12*f A friction'clutch 13 of any suitable type is provided for connectin the pulley 10 to the shaft 11.- rlhe friction clutch is controlled by a hand lever 14 which is mounted on a rod 15. The rod carries a. lever 416 havthe mechanism 20. The bevel gear wheel 19,

which meshes with the bevel gear wheel 18 on the shaft 11, iscarried by a shaft 23. A pinion 24 is mounted on the end of shaft 23 adjacent to the bevel gear wheel 19. '][`he4 pinion 24 is keyed to the shaft 23 for a purpose to be hereinafter set forth.v A twoway friction clutch 25, which is mounted on the shaft 23, is provided for transmitting power from the shaft 11 to a shaft 26. The clutch 25 carries two gear wheels 27 and 28. The gear 'wheel 27 meshes directly with a gear wheel 29 on the shaft 26 and the gear wheel 28 is connected to a gear wheel 30 on the shaft 26 through an idler gear wheel- 31. According to the position of the clutch 25, either the gear wheel 28 or the gear wheel 27 is directly connected to the 'shaft 23 and the bevel gear wheel 19. AAccordingly, the position of the clutch 25 determines the direction of rotation of the shaft 26.

yThe position of the friction `clutch y25 is automatically controlled by a cam drum 32. The cam drum 32 lis mounted on a shaft 33 and is operated under the control of a is mounted on a shaft 35 and comprises two end members 36 and 37 and a central member 38. The end members 36 and 37 are rotatably mounted on the shaft 35 and the central member v38 is splined to the shaft 35. The end member 36 carries -a gear wheel 39 which meshes with an idler-.gear wheel 39a. The gear wheel 39a meshes with a gear wheel 4() which is attached to the cam drum 32. The end member 37 carries a gear wheel 41 which meshes witha gear wheel 42 attached to the cam drum 32. A gear wheel 43, which is keyed to the shaft 35, meshes directly with the gear wheel 24 which is mounted on the shaft 23. Thus, when the teeth on the central member 38 of the jaw clutch engage the teeth on the end member 36, the cam drum 32 is rotated in one di- A suitable box 22 is atrection, and when the teeth on the opposite y gear wheel 24 on the shaft 23 are always in rotation when the friction clutch 13 is '1n Y an operative position.

, the box 22, as shown in Fig. 9 of the drawi'. two-,way clutch 25.

ings, carries a roller 45. The roller is fitted to a cam groove 46 on the cam drum 32. The lever 44 has a bifurcated end portion which is fitted to a groove 46 in the 1 Thus, the position of the two-way clutch 25 and accordingly the direction of rotation of the shaft 26 is controlled by the cam groove 46 on the cam drum 32. f

A'cam groove 48 is formed in the drum 32 for controlling the movement of the jaw clutch 34. A lever 49, which is'mounted on a shaft 50, carries a roller 51. The roller 51 is fitted to the groove 48. The opposite end of the lever 49 is fitted to a groove-52 in the central member 38 of` the jaw clutch 30. The shaft 5() not only carries the lever 49 but also has a lever 53 secured to it. The lever 53 is connected to a reversing rod 54. The reversing rod 54 is controlled, Vin

v a manner to be hereinafter set forth, in accordance with the movement of the carriage 2. When the carriage 2 is at either end of -its travel, the reversing rod 54 is operated for moving the central member 38 of the jaw clutch 34.

Referring to Fig. 7 of the drawings, it will be noted the cam groove 48 isso formed in the drum 32 as toinsure the movement of the drum in a direction'the reverse of the last movement. f The roller 51 on the lever 49 is shown in engagement with a shoulder 55 on the side of the cam groove. Accordingly, the reversing rod 54 can only be moved in -a direction to el'ect engagement between the central member 38 of the jaw clutch and the end member 36. Such movement with the jaw clutch will effect rotation of the drum 32 in a counter-clockwise direction, as shown in Fig. 9 of the drawings. The movement of the drum 32 is continueduntil the .roller 51 engages a shoulder 56 on the side drum 32, the central member 38 of thejaw clutch is moved away from the end member 36 to prevent any further movement thereof. In the last mentioned position of the drum, it will be noted the reversing lever 54 can only be operated in a direction to effect engagement between the central member 38 and the end member 37. yWhen the jaw clutch is so operated, it will be noted the cam drum 32 is operated in a clockwise direction'as shown in Fig. 9 of the drawings. As heretofore set forth, the'direction of -rotation of the cam drum 32 controls the direction of rotation of the shaft 26. However, the rotation of theshaft 26 is not stopped by the stopping of the rotation of the cam drum 32.

A- third cam groove 58 is formed in the cam drum 32 for controlling the relieving movements of the slide 21. A lever 59, which is mounted on a shaft61, vcarries a roller 60. The roller 60 is fitted to the cam groove 58. Theshaft 61,'which has a bearlng 1n the main frame 1, carries a second lever 62, as shown in Fig. 3 of the drawings. The lever 62 is connected by a link 63 to a cam slide 64. -The cam slide 64 is adapted to have vertical movement in the relieving slide 21 and serves to control the relieving movements as hereinafter set forth. f A spring member 65, which is secured to the end of thelever 62 exerts a-'force normally tending to hold the slide 64 in a raised )osition. It may be noted that in the raise position of the cam slide 64, relieving movements are effected by the slide 21 and a grinding wheel 66 is moved into engagement with a blank 67. Referringagainto Figs. '7, 8 and 9 of the drawings, the shaftv 26, which is controlled by the cam mechanism 20, carries a worm member 68. The worm member 68 meshes with a worm wheel 69 which is mounted on a cam shaft 70. The cam shaft 70 carries a cam member 71 which is adapted to .cooperate with a lug 72. The lug 72 projects from the cam slide 64, as shown .in Fig. 3 of the drawings.

A lever 73, which is pivotally supported y on the main frame 1 of the machine as shown in Fig. 3, is connected near the upper end thereof t0 the slide 125. The lower end of the lever 7 3 is connected toa s ring 74. The spring 74 is held and adjuste by a knob 75 which projects from the front of the machine. Thus, it is apparent the spring member 74 exerts a force` through the lever 73 tendin to move the relieving slide 21 away from t e blank carrying carriage. y

Assuming the cam slide 64 to be in the position shown in Fig. 3 of the drawings, the rotation of the-cam member 7l in av clockwise direction willv effect relieving movements by the slide 21. Inasmuch as the cam member 71 can only operate the relieving slide 21 when the lug 72 is in the raised position shown in Fig. 3, it is apparent when the slide 64 is lowered the relieving movements are automaticallv stopped. Not only are the relieving movements stopped. when the slide 64 is lowered, but the grinding wheel isl moved away from the blank. At the end of the grinding movement by the carriage 2, the cam drum 32 through the rod 61 and levers 59 rand 62 lowers the cam slide 64 to stop the relieving movements and moreover to withdraw the grinding wheel from engagement with the blank. `At the.v end of the return stroke by the carriage, the

cam slide 64 is raised not only'to move the lio grinding wheel into engagement with the blank but also to start the relieving movements.

The shaft 26, which carries the worm member 68 for operating the relieving slide, also carries a worm member 77 for not only rotating a blank carrying spindle 78 but also for operating the blank carrying carriage 2. The worm member 77 meshes with a worm wheel 79. The worm wheel 79 is splined to and slidably Imounted on a sleeve member 80. The sleeve member 80 is rotatably mounted on a carriage lead screw 81, as best shown in Figs. 1, 4, 5 and 6 of the drawings.

The sleeve member carries a gear wheel 82 which meshes with a gear wheel 83". The gear wheel 83 is supported on a slotted arm 85 by a stud bolt 84. The arm 85 is secured to a lug 86 vwhich projects from the carriage 2, as shown in Fig. f3 of the drawings. The arm 85 is secured to the lug 86 by means of two bolt-s 87 and 88 which project through a slot 89 in the arm as best-shown in Figs. 3 and 5 of ythe drawings. The gear wheel 83 meshes with a'gear wheel 89 which is mounted on ashaft- 90. The shaft 90 is provided with suitable bearings in the headstock of the machine and carries a gear wheel 91 which meshes with a v gear ywheel 92 on the spindle 78. The gear wheel 92 meshes with a gear wheel 93'which ismounted on a shaft1 94. The shaft 94 is provided with suitable bearings in the headstock and carries a second gear wheel 95. The gear wheel 95 meshes with a gearwheel 96 which is carried by a stud bolt 97. The stud bolt 97, which also carries a gear wheel 98, is mounted on the slotted arm 99. The arm 99 is pivotally supported by a bolt 100 and is held in position by a bolt 101. The stud bolt 97 projects through a slot 102 formed in the arm and the bolt 101 projects through an arcuated slot 103 which is formed in the arm. The gear wheel 98 meshes with a gear wheel 104 which is secured to the lead screw 81. Thus, it is apparent the train of gearl ing, which serves to rotate not only the blank grinding hobshaving right-handed threads.

ln case it is desired to grind hobs having left-handed threads, it is necessa to :re-4

verse the direction -,of rotation of t e screw 81. In order to reverse the direction ofrotation of the screw 81, an idler gear wheel 105 is interposed between the gear wheel 95 and the gear wheel 96. In Fig..4 of the 'dran/ings, the gear wheel 105 is shown su ported on an arm 106 by meansof a stud bot remise 107. The arm 106 is sup orted on the heady stock of the machine. en it isdesired to use the gear wheel 105 for reversing the direction of rotation of the lead screw 81,

f is supported in a bracket.112 as shown in Figs. 4 and 6 of the drawings.` The bracket 112 is secured 'to a web 113 of the main frame 1 by means of three bolts 114. Alever 115 is threadably connected to an end portion of the bracket 112 as shown in Fig. 4. The lever 115 isadapted to engage a washer 116 which is in engagement with a nut 117 on 'the Vend of the hub 110. By so rotating the-lever 115 as to wedge it against the washer 116, it is apparent the nut 108 is secured to the web 113, and thus is prevented from `rotating movement of the carriage 2. However, if the t knob 119 is pushed inwardly, the nut 108 is free' to rotate in the bracket 112. The worm wheel 109 on the nut 108 is rotated by means of a worm member 120 on a shaft 121 for adjusting the carriage 2 with respect to the grinding wheel. The shaft 121 is rotated.

by means of a hand wheel 122.

A feed shaft 123, which is manually operated by a hand wheel 124, is provided for operating an adjusting slide 125 transversely with respect to the lcarriage 2. The shaft 123 is provided with suitable bearings in the main frame 1 and carries a pinion 126 which meshes with a gear wheel 127. The gear wheel 127 meshes witha is mounted on a screw sha 129. The screw shaft 129 is rotatably supported in the relieving slide 21 and is connected to the adjusting slide 125 by means of a nut. 130. Upon referring to Fig. 3 of the drawings, it will be noted the gear wheel 127 is much wider than the pinion 128.1 By reason of the difference of vwidth lbetween the pinion and the gear wheel, the slide 21 may eiect relievin movements without separating the pinion rom th gear wheel.

A wheel base 131, which is mounte'don the mainframe 1 ofthe machine, serves to supinion 128 which of the relieving slide 21 has a slot 135 formed wheel 149.

therein, as shown in Fig. 12 of the draw.- in The camcslide 64 is mounted in the slot an'd is held in position by 'means of two plates 136, as shown in Figs. 3, 11l and 12 ofthe drawings. The slide 2l carries a pin 137, shown in Figs. 3 and 11 of the drawings, which projects through an opening 138 in a bracket 139 and engages a plunger 140. The bracket 139 is secured tothe wheel base 131 in anysuitable manner. The plunger 140 is resiliently held in the position shown in Fig. 3 by means of aspring member 141. The spring member 141 is .disposed between the head of the plunger 140 and a plug which vis secured to the late 139. The-pin 137 on the relieving sli e 21 cooperates with the resiliently supported plunger 140 to cushion the return movements of the relieving slide.

The adjusting slide 125 is mounted on ways 142 formed on the base member 131 and is held in position by suitable straps 143. The adjusting slide'125 carries a slide which is adjustable with respect to the slide 125. The slide 144 is fitted to a guideway 145 on the adjusting slide 125. The means for adjusting the slide 144 with respect to the slide 125 is best vshown in Figs. 11,'13 and 14 of the drawings. A small shaft 146, which projects from the side of theslide 144, carries an operating knob 147. The opposite end of the' shaft 146 carriesl a bevelv gear wheel 148 which mesheswith a bevel gear The bevel gear wheel 149 is mounted on a feed shaft 150. The feed shaft 150 is threadably connected to a nut 151 which is secured to the adjusting slide 125. Thus, it is apparent by operating the knob 147, the slides 144 and 145 are adjusted relative to olie another for varying the trans- Verse position of the grinding wheel with respect to the blank carried by the carriage 2. This mechanism is chiefiy used for dressing the wheel. Y

The slide-.144 carriesv a swiveling plate 153 which in turn carries the grinding wheel 66. The plate 153 is pivoted on a bolt 154 which projects from the slide 144. The plate 153 is heldin any adjusted position by means of a clamping bracket 155 which is shown in Fig. 3 of the drawings. The bracket 155 is clainped'to the plate 153 by means of two bolts-156 which are connected to the slide 144. Preferably a scale 157, as shown in Fig.

2 of the drawings, is formed'on the clamping bracket 155 in order to indicate the angular position of the swivelling plate 153. Two set screws 158, which project through arcuated slots 159, are also adapted to secure the swivelling plate 153 in any set position.` T wo upwardly projecting plates 160 and 161, whlch are preferably formed integral with the swivelling plate 153, are provided for supporting a vertically movable wheel slide .162. The wheel slide 162 is provided with a tongue 163, as shown in Fig. 2 of the drawings, which is fitted to a groove in either the plate 160 or the late 161. The Slide is secured to one of't 1e plates by means of bolts l164 which project through slots 165.

The grinding wheel 66 is mounted on a spindle 167 which has a bearing in the wheel slide 162. The spindle 167 also carries av ulley 168 which is connected by a suitable elt 169 to a pulley 170 on a shaft 171. The shaft 171 isprovided with bearings on arms 172 -whlch project from a plate 173. A pulley 174, which is mounted on the shaft 171 between the bearings, is connected ,to a suitable source of power..

The plate 173 .is provided with two sets of'notches 177 and 178, as shown in Fig. 2

of the drawings, for securing it by means of bolts 179 to the swivelling plate 153. Thev bolts 17 9 project through a slot 180, which ispulley 168. If the grinding wheel on the sllde 162 is supported on the plate 161, thev plate 173 is Secured to the plate 153 with the notches 178 in the plate 173 -aligned withy the slot 180 in the swivelling plate 153. The pulley 170 is placed on lthe end of the shaft 171'which will align it with the pulley 168 on the end of the wheel spindle 167. If the grinding wheel slide 162 iis changed from the plate 161 to the plate 160 for grinding the opposite sides of the hob teeth, the position of the plate 153 is reversed and the pulley 170 is changedto the opposite end ofthe shaft 171. By such means, the pulley 170 'is easily adjusted in line with the pulley 168 when the grinding wheel is mounted on the plates 160 and 161.

A bracket 182 is secured to the slide 144 by means of bolts 183. Two hand operated bolts 184 are provided for firmly clamping the bracket 182 in any set position. The bracket 182 carries an adjusting slide 185 having an adjusting plate 186 formed integral therewith. The adjusting slide is fitted to a guideway 187 formed in the bracket 182 and is held in position by two straps 188fand 189. A screw 190, which is operated by a knob 191. is supported in the slide 185. The screw 190'engages a nut 192 Vwhich is secured to the bracket 182. Thus` i shown in Fig. 15 of the drawings, carries scribed in a companion application of Carl i Schramm Serial No. 691,398 tiled February 8, 1924. One r of the dressing members is shown in dot and dash lines on the plate 194. By reason of the complete description given in the Schramm a plicati'on, it is deemed unnecessary to further describe the dressing of the wheel in this application.

, A pin 202, which projects from the top of the wheel slide 162, engages a lug 203 projecting from the bottom of the plate 186.

' Preferably, `the plate 186 is so positioned y that the pin 202 -on the wheel slide is in engagement with the lug 203 when the grindmg wheel axis is in the same plane as the axis of the blank. It may be noted that the reference plane throu h the axis of the wheel and the axis of the lank must be parallel to the plane of the relieving movements.

- When it is desired to elevate the grinding wheel with respect to the blank, the scale 204 and the markings on the knob 191'serve to accurately measure the position of the axis of the grinding wheel with respect to the axis of the blank.

The automatic operation of the carriage 2 l is controlled by two dogs 205 and 206. The

dogs 205 and 206 are held by bolts 207 and 208 in a slot 209 which is formed inthe carriage 2. The dog 206 has a lug 210 projecting 'from it. `T he lug 210 carries an adjust- 'ing bolt 211 which serves to control the amount of feedin a manner to be hereinafter set forth. A lever 212, which is rotatably mounted on al sleeve on the shaft 123, is positioned in alignment with the dogs 205 and 206. At the end of the -movement of the carriage 2in one direction, the lever 212 is operated by the dog 205 and at the end of the movement of the carriage in the o posite direction, the lever 212 is operated by the dog 206. The lever 212 is provided with two projecting arms 213 and 214. One of the arms 213 and 214 is connected by a rod 215 to a bellcrank lever 216. The bell crank lever 216 is pivotally mounted on the mainframe 1 and is connected to the reversing rod 54 as best shown in Figs. 1 and 2 of the drawings. When a hob having a right-hand thread is being ground, the rod 215 is connected to the arm 214 and when a hob having a left-hand l thread is being ground, it is necessary to connect the rod i 215 to the arm 213. The control of the cam mechanism 20 by the reversing rod 54 was described when reference was made to Figs.

ating the position of the reverse rod 54.

The plate 217 has a notch'218 formed init for cooperating with a spring pressed plunger 220. Referring to Figs. 7, 8, 9 and 10 of the drawings, a disk 239 is mounted ou the end of the cam drum 32 for accentuating' the extreme positionsy of such cam drum. Two notches 240 and 241 are formed in the disk 239 for cooperating with a spring pressed plunger 242. The plunger 242 is mounted in a lug 243 on the side of the box 22.

The automatic feeding of the grinding wheel 66 towards the blank 67 is controlled by a ratchet wheel 221. The ratchet wheel 221 is tixedly connected to the shaft 123 which operates the -feed shaft 129. A pawl 222, which .is mounted on a lever `223, is adapted to engage the teeth on the ratchet wheel. The lever 223 is rotatably mounted on a sleeve 224 which is mounted on -the frame of the machine. The lever -223 is so positioned as to be engaged by the` bolt 211 on the dog 206 near the end of the move- -ment of the carriage 2 towards the left as shown in Fig. 1 of the drawings. The lever 223 is provided with an` arm 225 which is positioned between ltwo set screws 226 and 227. The set Yscrews 226 andi227 are mounted on arms projecting from a bracket 228. The bracket 228 is secured to the main frame 1 and is provided with an arm 229 for su porting a reference pin ,230. A plate 2 31, w ich 'is rotatably mounted on the shaft 123-adjacent tothe hand wheel 124, carries *l a shield 232 which projects over the teeth on the ratchet wheel 221. A pin 233 projects through the plate 231 and engages the teeth` on theratchet wheel 221. The plate 231 is set ink any predetermined ,position with reference to the reference point 230 in order to stop the feeding movements after a predetermined feeding movement. The shield 232, which is mounted on the plate 231, is

moved after a predetermined feeding move-y ment to a position for separating the pawl 222 from the ratchet wheel 221.

A ccnterweight 235 is connected'to the carriage 2 by means of a flexible connection 236, as shown in F igs. 3 and 4 of the draw-l ings. VlThe counterweight maintains a constant pressure in one direction on the gearing which operates the carriage 2 and rotates the hob bla In a machine constructed in accordance with my invention, it will be noted the carriage 2 is automatically reciprocated in aci reached, of means for eiectin drawn from engagement with the blank during the movements of the carriage in one direction and is moved'into engagement with the blank during the movement of the carriage in an opposite direction. The rinding wheel is so mounted that it may e accurately positioned any desired distance above or below the axis of the blank in order to form involute surfaces on'the teeth of the hob being ground.

Modifications in the machine and inthe arrangement and location yof parts may be made within the spirit and scope of my invention and such modifications are intended to be covered by the appended claims. What I claim is: 1. In a machine for grinding hobs, the combination with a carriage having a blank mounted thereon, al grinding wheel, a slide for supportin the grinding wheel, means for rotating t e blank,- means for moving the carriage in one direction in accordance with the lead of the thread on the hob andthe rotation thereof, and means for auto' ma-tically returning the carriage to initial position when the end of the hob thread 1s movements by the slide in accor' ance with the movement of the carriage and for effecting relieving movements of the slide in accordance with the blank rotation, means for stopping' the relieving movements of the slide during the time the carriage is being returned to initial position, and mea-ns for so positioning the grinding wheel with respect'to the blank as to form involute surfaces on the blank teeth.

2. In a machine orgrinding' hobs, lthe combination with a carriage having a-blank mounted thereon, a grinding Wheel, a slide for supporting the grinding wheel, means for eii'ecting relieving 'movements by the slide in timed relation to the rotation of the blank, means for moving the vcarriage in accordance With the blank rotation to a predeterminedpoint and for automatically returning the carriage to initial position upon reachingsuch predetermined point, means for stopping the relieving movements and for holding the grinding wheel out of engagement with the blank when the carriage is being returned to initial position, and means or setting the grinding wheel axis a predetermined distance above the blank axis so4 that involute helicoids are cut on the side of the blank teeth.

8. In a machine for grinding hobs, the.

feeding combination with a rotating blank having teeth in thel form of a'. thread, a conical grinding 'wheel, and means for eiecting feeding' and relieving movements vby the wheel in timed relation to the blank rotation, of means for moving the blank longitudinally until a predetermined point is reached and then for automatically returning the blank to initial position, meansjfor automatically stopping the relieving movements during the return movement oflthe blank, and` means for varying the position of the wheel -axis with respect to the blank axis to eii'ect relieving movements bythe wheel in a plane outside the blank axis..

l4:. In a machine for grinding hobs, the combination `with a rotating blank having teeth in the form of a thread, a straight conical grinding wheel, and means for eiect.- ing feeding and relieving movementsv by the wheel in timed relation to the blank rotation, of means for moving the blank longitudinally in timed relation to the rotation thereof and for automatically returning the blank to initial position when the Wheel reaches the end of the hob thread, means for automatically stopping the relieving movements and for withdrawing the wheel from engagement with the blank during the return movement, and means for so positioning the wlieel with respect to the blank that the blank axis isnot included in the plane of the wheel relieving movements. A-

5. In a machine for grinding li'obs, the combination with a rotating blank having teeth in the form of -a thread, a straight Aconical grinding wheel, and means for effecting relative feeding and relieving movements between the wlieel andv the blank in timed relation to the blank rotation, of means for effecting relative movement between the wheel and the blank parallel to the blank axisiand in timed relation to the blank rotation, said last named means also serving. to' .return the blank and wheel to the initial relative position when the Wheel is at the end of the blank thread, means for` stopping the `relieving movements and for' separating the wheel and blank during said return movement, and means for so positioning the Wheel and blank as to cut yinvolute helicoids on the sides of the blank teeth.

6. In a machine tool, the combination with a blankcarrying carriage, a cutting tool, a relieving slide for carrying the tool, a rotating cam member for operating the relieving slide, and adjustable means for connecting 'to withdraw the tool from engagement with 'the blank.

8. vIn a machine for grinding hobs, the combination with a blank carryinv` carriage, a grinding wheel, a relieving slide for carrying the grinding wheel, arelieving cam, an adjusting slide mounted on the relieving slide and having a lug for engaging the relieving cam, and means for normally holding the lug on the adjusting slide and the cam in Aengagement with each other, 'of means for rotating the cam to ei'ect relieving movements by the wheel, and means for automatically withdrawing the lug on the adjusting slide from engagement with the cam in a predetermined position of the carnage.

9. In a machine for grinding hobs, the

combination with a blank carrying carriage,

a grinding wheel, a slide for carrying the grinding wheel, and means for exertmg a force tending to move the slide away from lthe blank, of a relieving cam for elfecting relieving movements by the slide, an adjusting slide having a lug thereon for .connecting the relieving cam to the relieving slide, means for movin the carriage in tim'ed relation to the blan rotation, means for automatically returning the carriage to initial position when the wheel is at the end of the blank, and automatic means for so moving .the adjusting slide during the return of the carriage as to separate the relieving cam from the relieving slide and permit the withdrawing of the wheel from engagement with the blank.

10. In a machine for grinding hobs, the combination with a blank y carrying carriage', a grinding wheel, a slide for carrying the grinding wheel, and resilient means for exerting a force tending to move the slide away from the blank, of a relieving cam for ell'eeting relieving movements by the slide,-

means for moving the carriage in timed relation to the blank rotation, means for automatically returning the carriage to initial position when the wheel is at the end of the blank, and automatic means for separating the relieving cam from the slide during the return movement of the carriage.

11. In a machine for grinding hobs, the combination with a blank carrying carriage,

a conical grinding wheel, a slide for carrying the grinding'wheel, a spring .operated lever for exerting a force tending to move the slide away from the blank, and a relieviing cam for operating the slide to effect relieving movements, of means comprising gearin for rotating the blank, for rotating the re ieving cam, for efecting feeding movements lb the slide, and for eii'ecting movements o the carriage, and means-comprising a cam drum for controllin the direction of movement of the carriage, ythe starting and stopping Qf therelieving movement and the posltion of the wheel with respect to the blank.

12. In a machine for grinding hobs, the

combination with a` carriage, and a slide movable vtransversely with respect to the carriage, of means for effecting relieving movements by the slide, automatic means for reciprocating the carriage with respect to the slide, and automatic means for starting the relieving movements when the carriage is moved in one direction and for stopping the relieving movements when the carriage is moved in an opposite4 direction.

'13. In a machine tool, the combination with a carriage, a slide movable transverse- 1y with respect to the carriage, and means for eccting relieving movements by the slide, of automatic means for reciprocating the carriage with, respect to the slide, and .automatic means-*for moving .-the slide toward the blank and for starting relieving movements when the carriage is moved in one direction and for stoppinfr the relieving movements and for moving tlie slide away from the carriage when the carriage is' movedin an opposite direction.

14. In a machine tool, the combination with a carriage, a slide-movable transversewith respect to the carriage, and means flir ei'ecting relieving movements -by the slide, of automatic means for reciprocating the carriagel with respect to the slide, automatic means for feeding the slide toward the carriage in accordance with the movement of the carriage, and automatic. means for starting the relieving movements' when the carriage is moved in one direction and for stopping the relieving movements when the carriage is moved Ain an opposite direction. A

15. In a lmachine tool, the combination with a carriage for supporting a rotating blank, and a slide for supporting arotating cutting tool, of means for eecting relieving movements by the slide with respect to the blank, automatic means for movingthe blank with respect to the tool and for returning the carriage to initial position when the blank and tool occupy predetermined relative positions, automatic means for stopping the relieving movements and for separating the tool from the blank' when the carriage is moving ,in one direct-ion, and for starting the relieving movements and moving the tool into engagement with the luf) blank when the agrriage is moved in an op-l posite direction.

16.. In a grinding machine, the combinatlon comprlsmg a`carr1age mounted on the mam frame of the machine, a feed nut lmounted on the main frame, a feed screw mounted on said carriage and co-aoting with lsaid nut tomove thecarriage, means on the carriage for supporting a, blank, means on the frame for locking said nut against movement, means on the frame for rotating the nut to move the carriage at will, and a, continuous set of gearing Voperated from the main frame for rotating' the blank and for operating saidfeed screw. 1

In testimony whereof, I hereto ax my signature.

' y CARROLL KNOWLES. 

